Anti-government protesters take cover near a truck after hearing gunshots during a clash with a pro-government group in Bangkok on Feb. 1, 2014. / Wason Wanichakorn, AP

by Thomas Maresca and James Monroe Adams IV, Special for USA TODAY

by Thomas Maresca and James Monroe Adams IV, Special for USA TODAY

BANGKOK - Violence erupted here Saturday on the eve of a deeply divisive national election, with a pitched gunbattle placing an already-tense city further on edge.

A firefight broke out near the Laksi District Office in the northern part of the Thai capital Saturday afternoon between anti-government protesters, known as the People's Democratic Reform Committee (PDRC), and pro-government red shirt factions. The melee left at least seven wounded, including an American photojournalist.

The PDRC group had been blocking the entrance to the district office, which holds paper ballots for Sunday's election. The protesters oppose the election going forward without first instituting reforms of a political system they say is deeply corrupt.

The two groups met near a large intersection where highways, local roads and train tracks converge beneath an overpass. After shouting and posturing, a pair of explosions were heard, followed by a gunbattle that left bystanders and journalists ducking for cover. It is unclear who fired first.

Saturday's violence is the latest round in a series of protests that have left 10 dead and nearly 600 wounded since the beginning of November. Last weekend, a protest leader was shot and killed in broad daylight and another 11 were wounded as early voting was disrupted at many locations around Bangkok.

The unrest has raised fears that Sunday's election - which was called after embattled Prime Minister Yingluck Shinawatra dissolved parliament on Dec. 9 - will be even more violent.

Sean Boonpracong, a government security adviser, said Saturday's clashes send a troubling signal for Sunday's election. "We are wondering if this is going to be a pattern tomorrow," he said.

Police said they will deploy 100,000 officers nationwide, while the army is putting 5,000 soldiers in Bangkok to boost security. More than 47 million people are registered to vote.

"How did we get to this point?" asked Chanida Pakdeebanchasak, a 28-year-old Bangkok resident who was determined to cast her ballot Sunday. "Since when does going to vote mean you don't love the country?"

Thiti Iamsumang, 21, an emergency responder on the scene Saturday, said he has been on the job for a couple of weeks and has already seen more violence than he could have imagined.

His first day of work was Jan. 17, when he responded to an explosion that killed one person and left dozens injured. Saturday's incident left him shaking his head. "This is not OK for Thailand," he said. "I want peace."